The present invention relates to a projection-type vehicular headlamp in which a light projecting unit, which includes a light source, a substantially ellipsoidal reflector, and a projecting lens, is mounted in a lamp chamber defined by a lamp body and a front lens. More particularly, the invention relates to a projection-type vehicular headlamp in which the lamp body has a light source attachment opening formed in its rear end wall.
A conventional vehicular headlamp of this type is constructed as shown in FIG. 5. That is, a light projecting unit 3 is mounted in a lamp chamber defined by a lamp body 1 and a front lens 2. The light projecting unit 3 includes a light source, namely, a light bulb 3a, a substantially ellipsoidal reflector 3b in which the light bulb 3a is fitted, and a projecting lens 3d connected through a lens holder 3c to the reflector 3b. The output light beam of the light bulb. reflected from the reflector 3b is converted into a substantially parallel light beam by the projecting lens 3d, which beam advances forwardly of the headlamp. The light bulb 3a is inserted in a bulb fixing hole formed in the rear wall of the reflecting mirror 3b from behind. More specifically, the light bulb 3a is engaged with or disengaged from the bulb fixing hole through a bulb attachment opening 1a formed in the rear wall of the lamp body.
On the other hand, recently there has been a demand for miniaturization of vehicular headlamps dictated by styling demands. In order to meet this requirement, the lamp body 1 is set as close to the light projecting unit 3 as possible. However, since the bulb attachment opening is formed in the rear wall of the lamp body 1, the latter is liable to be deformed by external forces.
Further, in a projection-type vehicular headlamp, the light beam from the light source is concentrated before projected, and hence the light projecting unit 3 is considerably high in temperature. In spite of this fact, the bulb attachment opening la in the rear wall of the lamp body is covered with a rubber cover 6; that is, the lamp chamber is closed. This results in a difficulty in that, since the lamp body 1 is reduced in size, the lamp chamber around the heat source, namely, the light projecting unit 3, is decreased in volume, and accordingly the lamp body is more liable to be affected by heat. That is, when the headlamp is turned on, the lamp body is increased greatly in temperature by the heat generated by the light projecting unit, as a result of which the lamp body 1 may be deformed. Accordingly, the material of the lamp body is limited; that is, it is necessary to use a material high in heat resistance to manufacture the lamp body.